1. Field of the Invention
Our invention is adapted for use as a thrust-journal bearing in the main thrust position of an internal combustion engine, compressor, or similar device, for supporting a rotating crankshaft. Such a bearing is constantly being subjected to axial and radial loads of varying magnitude. The journal bearing portion supports the radial loads which are induced by firing, compression, inertia, and gravity while the thrust washer portion accepts or absorbs the axial loads generally resulting from acceleration, deceleration, clutch disengagement, et cetera.
2. Description of the Prior Art
In the early days of development of the plain bearings, as our type of bearing is generally referred to in distinction from anti-friction bearings of the ball and roller type, it was found that compatable metallic alloys of different hardnesses gave improved performance when mated together with a continuously separating oil film. In most cases the journal was a steel shaft and the non-rotating mating surface of the bearing was usually some alloy of tin, copper, and antimony known as babbitt metal. Plain bearings were made by melting the babbitt metal and casting it directly into a bearing recess where it was allowed to harden before it was machined to the proper size. If a flanged bearing was required for accepting thrust loads as in our invention, it was also cast from the same pour to form an integral bearing unit. Alternatively, the thrust portion was cast as a separate piece and generally connected in some manner to the journal bearing. While there appears to be no particular development trend in the patent art it was known to use dowels or pins as an interlocking means such as shown in U.S. Pat. No. 2,177,565 issued in 1939 and it was also known to use a cast lug on the thrust flange for interlocking with a corresponding groove or depression formed in the upper journal as shown in U.S. Pat. No. 734,171, issued in 1903. It is believed that by far the most conventional type was the pinned bearing unit. These units performed well. The journal bearing portion was over designed but provided a good bearing surface and was sufficiently flexible for yielding to whatever extent necessary to absorb the higher loads. Likewise, the thrust washers were in some instances replaceable apart from the sleeve portion and without having to disassemble the crankshaft from the engine block. However, under the demands of mass production there was developed, beginning in the early 1940's, bimetallic bearing strip, made of a comparatively thick piece of sheet steel to which a comparatively thin layer of bearing alloy has been sintered, as shown in U.S. Pat. No. 2,986,464, previously owned by the assignee of the present invention. This type of bearing was fabricated from such strip with the thrust flange being either stamped or roll formed. With this the advantages of the multipiece thrust-journal bearing were lost. More recently, economic conditions, including high material costs and bearing replacement labor costs have again forced consideration of the multipiece combination thrust and journal bearing. U.S. Pat. No. 3,713,714 is one indication of renewed recognition of the need for such a bearing. Our invention offers an improvement over all the prior art known to us in both cost and ease of assembly and disassembly.